Hard disk drives are common information storage devices. FIG. 1 provides an illustration of a typical disk drive unit with a typical drive arm 104 configured to read data from and write data to a magnetic hard disk 101. Typically, a spindling voice-coil motor (VCM) is provided for controlling the motion of the drive arm 104. The top of the drive arm 104 has a suspension 105 mounted thereon, which supports a slider 103 with a read/write transducer (not show). When the disk drive is on, a spindle motor 102 will rotate the disk 101 at a high speed, and the slider 103 will fly above the disk 101 due to the air pressure drawn by the rotated disk 101. The slider 103 moves across the surface of the disk 101 in the radius direction under the control of the VCM. With a different track, the slider 103 can read data from or write data to the disk 101.
As consumers constantly desiring greater storage capacity for such disk drive devices, as well as faster and more accurate reading and writing operations, different methods are used to improve the recording density of information recording disk drive unit. At the same time, different methods are also widely utilized to achieve higher head positioning precision.
One methodology for the head accuracy position control with the small track pitch is implementing dual stage actuator (DSA). A second micro-actuator is being utilized to control the slider with the read/write head, with the first VCM utilized for course adjustment and the micro-actuator then correcting the placement on a much smaller scale to compensate for the resonance of the VCM. This enables a smaller recordable track width, increasing the ‘tracks per inch’ (TPI) value of the disk drive unit by 50%, which increases the density.
Another technology for head position control is to sense and compensate the air turbulence which is due to air flutter when the disk is being spindled. The air turbulence may cause the head suspension vibration which will cause the head off-track, as disclosed in US patent No. 20080229842. FIGS. 2b-2c show respectively cross-section reviews taken along line 6-6 and 7-7 in FIG. 2a. Referring to FIGS. 2a-2c, a load beam 11 is coupled with a base plate 10. A flexure 12 having a slider 13 mounted thereon is welded to the load beam 11 and the base plate 10. A vibration sensor 14 is mounted on the hollow portion of the load beam 11 by an adhesive. The vibration sensor 14 is a PZT unit which has a upper electrode 23, a lower electrode 24 and a PZT material 25 sandwiched therebetween, and two electrode terminal pads 18 and 19 of the vibration sensor 14 are connected with suspension traces 20 of the flexure 12 by conductive adhesive 28 and 27, respectively. When a vibration happens, the vibration sensor 14 will sense the suspension vibration in the suspension elastic port 22 and generate a signal. According to this signal, the position of the slider 13 can be adjusted.
FIG. 3 illustrates a side elevational view of a HGA shown in FIG. 2a. In FIG. 3, it is clear that the vibration sensor 14 is mounted at the juncture of the base plate 10 and the load beam 11, which is the suspension forming location. Since the vibration sensor 14 is located in the suspension hinge location, it has lower sensitivity for sensing the vibration of the suspension, much less the slider 13. Further, during the manufacture process of the suspension and the HGA, since per gram load and pitch static angle/roll static angle (PSA/RSA) need to be controlled, the suspension have to go through a pre-forming process, which may cause damage to the vibration sensor 14.
Accordingly, it is desired to provide an improved vibration sensor for a HGA to overcome the above-mentioned drawbacks.